Chang Haonan's subconscious complaint just now naturally aroused a burst of curiosity.

"Dr. Chang has seen a similar design before?"

Someone from the conference room asked curiously.

"That's not true, I can only think of it as having some understanding." Chang Haonan hurriedly went back to make up for it:

"This three-section slat, which is more suitable for the French fighter with a tailless delta wing layout, works together with the two-section lifting ailerons on the trailing edge to guide the airflow to form a vortex between the wing root and the vertical tail."

"But our J-8-2 is a conventional layout, and there is a horizontal tail wing behind, the advantages of this design cannot be brought into play, but it increases the resistance and dead weight for no reason, and it is normal for the effect to be bad, no wonder Mr. Yang just said that this design is too complicated."

After hearing this judgment, many people also nodded in agreement.

When I cooperated with Dassault in the mid-80s, the Chinese aviation industry at that time could only be said to have just begun to try to really "design" rather than just copy a fighter jet, and many things were indeed blank, but at this time in 1996, everyone had some experience and could naturally see the problem with this program.

Yang Fenghata stood up and came to the two boxes containing materials, and very skillfully took out a relatively new design document from it and handed it to Chang Haonan:

"Complexity is secondary, after the French withdrew, we also tried to make some improvements, only retaining the two sections of the three-section slat on the outside of the wing, and then changing the structure to an ordinary one-stage type, so that the dead weight is down, but the interference problem between the aileron and the flaps just mentioned is still not solved."

Chang Haonan opened the thick document, judging from the date of 1990 marked on it, it should be the improvement part that Yang Fengfa said.

But by this time, he had basically made a judgment about the problem.

Although the application of the leading edge slats has a long history, as a relatively simple and crude lifting device, aircraft designers have long focused on two main points: the length of the slats and the position of the slats.

Of course, this is mainly due to the fact that before the mid-90s, there was really no place to do too much detailed research on complex flow fields, and everyone only knew the basic principles of the slat, and the effect that could improve low-speed maneuverability and high angle of attack performance.

Another half an hour passed, Chang Haonan directly skipped the calculation design part, and finally found what he wanted in the final wind tunnel test data.

"Mr. Yang, I can do this slit design!"

He closed the design document and put it back in its original position in the data box, then raised his head and looked at Yang Fenghata beside him:

"However, I'm afraid it's not enough just to use the conditions of our 601 Institute."

"None of the conditions of the 601 Institute are good?"

Liu Ming next to him couldn't help but widen his eyes.

"Yes, from the design document that Mr. Yang just took out, we can summarize several main problems in the design of the slat."

Chang Haonan turned around and walked to the blackboard again, only this time he picked up a piece of chalk, and then flipped the blackboard to the side where there was nothing pasted:

"First, for multi-segment airfoils with large flap declination angles, even if the incoming Mach number is not high, there may be limited supersonic flow on the upper surface of its leading edge, and there is interference in the transonic region and shock boundary layer, in other words, even if the slat will only start in the subsonic state, it will still involve the most complex transonic flow field simulation."

"The second is that the wake of the upstream segment is often mixed with the boundary layer on the surface of the downstream segment, and the synthesized shear layer is a hybrid boundary layer for which there is no ready-made empirical formula to use."

"Thirdly, and most importantly, when the trailing edge flap is deflected, a separation bubble forms at the trailing edge of the main wing. If the leading edge slats are deflected at the same time, then the hybrid boundary layer and the flow separation occur at the same time, i.e., there is an interference between the two lifting devices at the leading and trailing edges. ”

Chang Haonan drew a classic three-section wing model of the leading edge-main wing-trailing edge as he spoke, and then began to mark the flow conditions involved in the upper surface of the wing when the two devices work together.

"This is indeed the case, especially the third point you mentioned Comrade Xiao Chang, which we were not able to figure out when we summed up the lessons and lessons at that time."

Yang Fenghata nodded with emotion, on the one hand, he remembered the difficulties encountered when designing this leading edge slat, and on the other hand, he was amazed that Chang Haonan was able to condense the most critical issues in the entire design in such a short time.

Being able to find the main problem from the complex reality is already a very rare ability in itself.

"So, since there is interference between the slit and the flap, it may not be enough to improve the former."

Chang Haonan drew a circle on the model of the wing he had just drawn, and continued:

"I am going to treat the two as a whole, carry out a more detailed integrated design, and comprehensively consider the five variables of trailing edge flap deflection angle, trailing edge flap chord length, leading edge slat deflection angle, overlap amount, and slit width, and overturn the whole scheme overall."

"In addition, after the design is completed, I also plan to consider adding a group of parallel vanes to the trailing edge of the leading edge slat as a flow deflector, so as to channel the incoming energy into the vicinity of the wing surface, increase the anti-separation ability of the wall boundary layer, and further inhibit the occurrence of stall phenomenon."

"But in this case, it is necessary to solve the Reynolds average N-S equation numerically for CFD simulation, which is very computational, and it may take a long time to get the results by relying only on the workstations in the computing center, so I hope that the research institute will come forward and apply for the use of a supercomputer!"

At the conference table not far away, Yang Fenghata leaned back in his chair and looked at Chang Haonan, who was holding chalk in his hand and was in high spirits.

For the first time, he felt that perhaps he was getting old.

It's not because of how well the body functions, but because of ......

The sharpness of my youth is less.

According to his idea, since the No. 10 and No. 11 projects are already advancing rapidly, it is enough for the J-8-3 to be responsible for the high-altitude and high-speed volley missions that he is good at.

But Chang Haonan is obviously not satisfied with this.

He wanted to optimize the aircraft in all aspects, which was essentially obsolete before it entered service.

To this end, the existing wing design was changed in a large area.

Tear down and start over.

For designers in any field, it is quite courageous to dare to say these four words.

Behind this lies a myriad of workloads, risks, and responsibilities.

Yang doesn't like risk.

But this time, he was a little moved.

Moreover, from the first time he heard the name Chang Haonan to the present, the other party has shown miraculous ability many times, which is also an important bargaining chip that affects Yang Feng's judgment.

Of course, for such a serious and high-impact decision, you still have to ask what you should ask clearly.

"So what kind of technical approach are you going to use to complete this integrated design of slat-flap?"

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